The present invention relates to light beam projecting devices and more particularly to a self-leveling laser beam projector particularly useful for construction, surveying, tunnelling and like applications.
Self-leveling laser devices are known in the prior art; however, they are extremely bulky in size and require generally a great number of components such that when the assembly is mounted, the light beam output will attain a true horizontal or a vertical position. Such prior devices have not been generally acceptable for field use as the extremely sensitive components required to provide the self-leveling feature will not withstand the extreme field conditions to which they were subjected. In some prior devices for maintaining a vertical or horizontal beam, the sensing components included gyroscopes, liquid lenses, pendulously supported light sources, and the like in an attempt to provide a true horizontal or vertical output beam. Additionally, in all prior art self-leveling projectors known to Applicant, the vertical, or horizontal, if a system of mirrors and/or prisms is used at the output, beam can only be provided in one plane of movement of the source. That is, if the projector is moved, for example, in a fore and aft direction and a vertical output is maintained, the apparatus will not accurately respond to movement to the left or right.
Typical examples of prior art systems for automatically maintaining a beam of light along a horizontal axis are illustrated in Mason et al, U.S. Pat. No. 3,729,266 issued Apr. 24, 1973, entitled APPARATUS FOR AUTOMATICALLY DIRECTING AND MAINTAINING A BEAM OF ELECTROMAGNETIC RADIATION RELATIVE TO EARTH HORIZONTAL; Bird et al, U.S. Pat. No. 3,748,041 issued July 24, 1973, entitled LASER BEAM ATTITUDE CONTROL DEVICE; and Zoot, U.S. Pat. No. 3,684,381 issued Aug. 15, 1972, entitled LASER BEAM PLANAR REFERENCE.
Each of the above-referenced patents, however, while providing means for attaining self-leveling of a horizontally projected laser beam suffer from one or more inherent drawbacks. Typically, in the gimbal-mounted systems, a series of lenses is required and some form of interconnection must be provided between the several lenses to provide the necessary compensation to correct for the additive effects of the angles of incidence and reflection. Alternately, as in the case of Zoot, no such correction is made and special outside compensation means as a prism must be provided. In addition, none of these systems readily lend themselves to a simple modification wherein the output therefrom can be used to project a horizontal plane, a vertical plane, a sweeping horizontal plane, nor can they be conveniently adapted for projection of a beam along a horizontal plane in a conventional manner.